Longitudinal Trends in Vaccine Hesitancy in a Cohort of Mothers Surveyed in Washington State, 2013-2015.

Parents who refuse or delay vaccines because of vaccine hesitancy place children at increased risk for vaccine-preventable disease. How parental vaccine hesitancy changes as their children age is not known. In 2015, we conducted a follow-up survey of 237 mothers enrolled in a 2-arm clinic-level cluster randomized trial (n = 488) in Washington State that was completed in 2013. We surveyed mothers at their baby's birth, age 6 months, and age 24 months using a validated measure of vaccine hesitancy. Both mean hesitancy scores (mean 4.1-point reduction; 95% CI, 2.5-5.6; P = .01) and the proportion of mothers who were vaccine hesitant (9.7% at baseline vs 5.9% at 24 months; P = .01) decreased significantly from child's birth to age 24 months. Changes from baseline were similar for first-time mothers and experienced mothers. Individual item analysis suggested that the decrease may have been driven by increases in maternal confidence about the safety and efficacy of vaccines. Our results suggest that hesitancy is a dynamic measure that may peak around childbirth and may remit as experience with vaccines accumulates.